Static accumulation during calibration of extruded thermoplastic foam board is common, and the discharge of this static can often lead to localized fires, particularly when using flammable blowing agents to expand the foam. Combustion of the blowing agent is a significant process upset and is also undesirable from many safety and operational perspectives.
Static dissipative measures could be attempted, including non-contact devices such as air ionizers, but such measures have limited effectiveness based on access to the board being restricted by the calibrator itself. Physical measures may also be deployed, but the board changes geometry and dimension during startup, so it is difficult to maintain contact with the foam without the foam damaging mechanical devices.
There has been a long felt need for the invention, in part, because the use of systems that do not provide the desired lubricity and static dissipation properties has resulted in manufacturing processes that are inefficient and that are prone to fires.